In Rutherford's famous scattering experiments that led to the planetary model of the atom, alpha particles with charge of +2e and masses of 6.64*10^-27 kg were fired at gold nucleus with charge of +79e. An alpha particle, initially very far from the gold nucleus is fired at speed of v(i)=2.0*10^7 m/s directly toward the nucleus. How close does the alpha particle get to the gold nucleus before turning around? Assume gold nucleus is static and energy is conserved.